Polyurea-Urethane Cord Treatment for Power Transmission Belt and Belt

ABSTRACT

A belt with a tensile cord embedded in an elastomeric body, having a polyurea-urethane adhesive composition impregnating the cord and coating the fibers. The composition is reaction product of a polyurethane prepolymer and a diamine curative. The prepolymer is a reaction product of a compact, symmetric diisocyanate and a polyester, polyether, or polycarbonate polyol. The belt body may be of cast polyurethane, vulcanized rubber, or thermoplastic elastomer. The cord may have an adhesive overcoat.

BACKGROUND OF THE INVENTION Field of the Invention

This invention relates generally to a method of treating tensile cordfor a power transmission belt, the treatment, the cord and the resultingbelt, more particularly to polyurea-urethane-treated carbon fiberreinforcement, and specifically to a carbon fiber cord impregnated witha moisture-cured polyurea-urethane composition.

Description of the Prior Art

U.S. Pat. No. 5,807,194 to Knutson et al., the contents of which arehereby incorporated herein in its entirety, discloses a synchronouspower transmission belt with a belt body of cast urethane belt material,belt teeth formed of the body, a wear-resistant fabric reinforcementdisposed along peripheral surfaces of the belt teeth, and a tensilemember of helically spiraled cord embedded in the belt body and of ayarn of carbon fiber, wherein there are interstices between the fibersof the cord and belt material penetrates at least a portion of the cordinterstices as the belt is cast so that the cord interstices contain aminimum of about 0.21 mg of belt material per mm³ of cord volume.Penetration of polyurethane elastomer into the cord may give excellentphysical adhesion. However, urethane in its cured state as a highmodulus belt material may make a particular cord material unacceptablewhen it penetrates the interstices of the cord because the so penetratedcord may have an unacceptably high bending modulus. Also, thepenetrating urethane may transfer too high a strain to filamentscomprising the cord and thus cause unacceptable filament breakageresulting in cord failure. Cast polyurethane materials are often of sucha viscosity that it is hard to sufficiently impregnate the cord.Problems from insufficient impregnation include fraying of cord, poorfatigue life, etc.

U.S. Pat. No. 5,231,159 to Patterson et al., the contents of which arehereby incorporated herein in its entirety, describes cast or RIMpolyurethane compositions useful for belts. The polyurethanes are basedon the reaction product of an isocyanate-terminated (preferablypolyether) prepolymer, an amine- or hydroxyl-terminated polyol, and apolyamine or polyol chain extender.

U.S. Pat. No. 6,964,626 to Wu et al., the contents of which are herebyincorporated herein in its entirety, discloses improvedpolyurethane/urea elastomers having high temperature stability to about140-150® C. and low temperature flexibility at about −35-(−40)° C., foruse in dynamic applications. These elastomers are useful for applicationin belts, specifically in automotive timing or synchronous belts,V-belts, multi-V-ribbed or micro-ribbed belts, flat belting and thelike. The polyurethane/urea elastomers are prepared by reactingpolyisocyanate prepolymers with symmetric primary diamine chainextenders, mixtures of symmetric primary diamine chain extenders andsecondary diamine chain extenders, or mixtures of symmetric primarydiamine chain extenders and non-oxidative polyols, which are all chosento eliminate the need for catalysts via standard molding processes, andto improve phase separation. The polyisocyanate prepolymers are reactionproducts of polyols which are nonoxidative at high temperatures, such aspolycarbonate polyols, polyester polyols, or mixtures thereof, withorganic polyisocyanates which are either compact, symmetric andaromatic, such as para-phenylene diisocyanate, 1,5-naphthalenediisocyanate, and 2,6-toluene diisocyanate, or are aliphatic and possesstrans or trans,trans geometric structure, such as trans-1,4-cyclohexanediisocyanate and trans,trans-4,4′-dicyclohexylmethyl diisocyanate.

Prior efforts to treat cord with a softer material to make a moreflexible cord in polyurethane belts have resulted in belts with lowertorque resistance, higher heat build up during flexing, poor resistanceto delamination, and the like. Adhesive treatments for carbon fiber cordin general have been less than adequate for demanding belt applications,whether for polyurethane or rubber belts. Representative of prior carbonfiber adhesive treatments are U.S. Pat. Nos. 6,695,733 and 6,945,891 toKnutson, which disclose a toothed rubber belt withresorcinol-formaldehyde-latex (“RFL”) treated carbon fiber tensile cord.Also representative of the carbon fiber adhesive art is the epoxy primerand RFL treatment of U.S. Pat. No. 4,044,540 to Toki et al., and theprimer and RFL treatment of U.S. Pat. No. 4,978,409 to Fujiwara et al.

U.S. Pat. Appl. Pub. No. 2005-0271874A1 to Sakajiri et al. disclosescarbon fiber sizing treatment with unsaturated urethane compound as theprincipal component. JP 2005-023480A2 to Sakajiri et al. discloses aresin composition including a polyurethane, an epoxy resin and acrosslinking agent for impregnating a carbon fiber bundle.

U. S. Pat. Pub. No. 2009/0098194A1 describes urea-urethane chemistry.

U.S. Pat. No. 3,962,511 discloses polyurethane compositions forencapsulating textile woven fabric for industrial conveyor belts and amethod of applying a polyurethane reaction mixture in an organic solventsolution.

Reference is made to co-pending application Ser. No. 11/947,470 filed onNov. 29, 2007, and Ser. No. 12/044,957 filed on Mar. 8, 2008, thecontents of both of which are hereby incorporated herein in theirentireties.

SUMMARY

The present invention is directed to systems and methods which provideflexible, high-modulus tensile cords for reinforcing belts and dynamicrubber articles, including polyurethane power transmission belts andrubber drive belts. The present invention provides a cord with goodadhesion and compatibility with polyurethane belt body materials andwith improved handling including excellent tensile strength, reducedfraying or fly build up, and durability. Polyurethane belts accordingthe invention have improved flexibility for enduring handling, backbending, and the like, and improved cutting performance. Rubber beltswith carbon tensile cords according to the invention exhibit improvedperformance over conventional RFL-treated carbon cord. The invention isdirected to cords with an adhesive treatment that can be applied to atwisted bundle of fibers with good penetration into the bundle.

The present invention is directed to a belt with a tensile cord embeddedin an elastomeric belt body with the cord having a polyurea-urethane(“PUU”) adhesive treatment. The PUU adhesive may be based on apolyurethane prepolymer, such as a polyester or polyether orpolycarbonate, terminated with isocyanate, having been derived from apolyol reacted with a diisocyanate. The polyester may bepolycaprolactone. The polyol may be a mixture of diol and triol. Thediisocyanate may be a symmetric, compact diisocyanate, such as PPDI,TDI, MDI, and the like. The diisocyanate may not be perfectly symmetric,but preferably is. The adhesive treatment may have a compact, symmetric,diamine curative or may be cured with water, such as environmentalmoisture. The invention is also directed to the tensile cord and theadhesive composition.

In an embodiment of the invention, the tensile cord may be based oncarbon fiber filament yarn, which may be twisted before impregnationwith the adhesive. The interstices between the fibers, regardless offiber type, may be partly or completely filled with the adhesive. Thefibers may be coated with the adhesive. The filling may be from 20% to99% or 100% of the volume of the interstices. Though the fibers may becoated and some interstices filled with adhesive, the coating may berelatively thin and not enough to completely bind all the fiberstogether. In an embodiment using cast polyurethane for the belt bodymaterial, the cast polyurethane may impregnate some or all of theremaining interstices and intimately contact the adhesive coating.Alternately, the cord may have an additional overcoat adhesive.

The invention is also directed to a method including the steps of makingan adhesive dip by mixing or dissolving the polyurethane prepolymer in asuitable solvent along with a small or compact, symmetric, diaminecurative, dipping a yarn or twisted yarn into the dip, drying off thesolvent, and at least partially curing the adhesive. The curative may bewater alone which may be available from ambient moisture present in thesolvent and/or air. During cure, urea linkages form between isocyanateend groups on the prepolymer molecules. The prepolymer may be linear(two isocyanate ends) or branched (three or more isocyanate end groups)(preferably just two or three or mixtures thereof).

The foregoing has outlined rather broadly the features and technicaladvantages of the present invention in order that the detaileddescription of the invention that follows may be better understood.Additional features and advantages of the invention will be describedhereinafter which form the subject of the claims of the invention. Itshould be appreciated by those skilled in the art that the conceptionand specific embodiment disclosed may be readily utilized as a basis formodifying or designing other structures for carrying out the samepurposes of the present invention. It should also be realized by thoseskilled in the art that such equivalent constructions do not depart fromthe spirit and scope of the invention as set forth in the appendedclaims. The novel features which are believed to be characteristic ofthe invention, both as to its organization and method of operation,together with further objects and advantages will be better understoodfrom the following description when considered in connection with theaccompanying figures. It is to be expressly understood, however, thateach of the figures is provided for the purpose of illustration anddescription only and is not intended as a definition of the limits ofthe present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and form part ofthe specification in which like numerals designate like parts,illustrate embodiments of the present invention and together with thedescription, serve to explain the principles of the invention. In thedrawings:

FIG. 1 is a fragmented perspective view, with parts in section, of atiming belt constructed in accordance with an embodiment of the presentinvention;

FIG. 2 is a fragmented perspective view, with parts in section, of aV-belt constructed in accordance with an embodiment of the presentinvention;

FIG. 3 is a fragmented perspective view, with parts in section, of amulti-V-ribbed belt constructed in accordance with an embodiment of thepresent invention;

FIG. 4 is a schematic of a flexibility test used to test acharacteristic of a belt embodiment of the invention.

DETAILED DESCRIPTION

The present invention is directed to a polyurea-urethane (“PUU”)adhesive composition for use on textile fibers, and in particular forpreparing treated tensile cord for use in reinforced rubber articlessuch as belts or hose. The PUU adhesive is based on a urethane-linkedprepolymer which is then cured with amines or water to form urealinkages. The PUU adhesive may be preferably moisture cured, rather thanbeing amine-cured. The PUU adhesive may be preferably based on aprepolymer of para-phenylene diisocyanate (“PPDI”) and apolycaprolactone (“PCL”). The PUU-treated cord is particularlyadvantageous in polyurethane (“PU”) and/or PUU belting or otherpolyurethane articles, whether cast elastomer or thermoplasticelastomer. With a suitable overcoat adhesive, the PUU-treated cord isalso suitable for use in rubber belting, hose, or other vulcanizedrubber articles. The fiber of the treated cord may preferably be carbonfiber.

The PUU adhesive may be based on a polyurethane prepolymer, such as apolyester or polyether or polycarbonate terminated with isocyanate. Suchprepolymers are made by reacting a polyisocyanate, with a polyol (i.e.,an hydroxy-terminated polymer, a diol and/or triol preferably).Preferably the polyisocyanate is a symmetric, compact diisocyanate, suchas PPDI, 2,4- and/or 2,6-toluene diisocyanate (“TDI”), 4,4′-methylenediphenyl diisocyanate (“MDI”), etc. The polyisocyanate may not beperfectly symmetric, but preferably is symmetric. The PU prepolymer maythen be dissolved in a suitable solvent along with small or compact,symmetric, diamine curative/chain extender or with water alone which maysimply be available from ambient moisture present in the solvent and/orthe air, which after drying the solvent, react to form urea linkagesbetween isocyanate end groups on the prepolymer molecules. Theprepolymer may be linear (i.e. with two isocyanate end groups) orbranched (i.e. with three or more isocyanate end groups), but ispreferably with just two or three isocyanate end groups or mixtures orblends thereof. The urea linkages/segments aggregate to formhard-segment domains interspersed throughout a soft segment matrix ofpolyester, polyether, etc. For a belt cord application, it has beenfound advantageous to make the adhesive softer than the belt bodymaterial, so small, compact curatives are preferred. The most preferablecurative is water, giving the smallest hard segment and therefore thesoftest PUU adhesive. The most preferable soft segment for beltapplications is a polyester such as polycaprolactone because of itsexcellent heat resistance, tear resistance, etc. Polyethers generallyhave a lower tear resistance than polyesters. Resistance to tear can bevery important in reinforced rubber articles such as belts, especiallyat the interface between the cord and the body of the article or thetooth compound of the belt. The most preferable diisocyanate for beltapplications is PPDI because of its thermally stable linkages, andbecause it has the best reactivity with water, the preferred curative.Cords made with the preferred PUU are extremely flexible after beingdipped or treated, and thus partially or fully impregnated with PUU. Asa result, the treated cords exhibit minimal handling damage duringprocessing and end use, and they bond well to various cast PU or PUUbelt body formulations, to thermoplastic elastomers (“TPE”s), andthermoplastic polyurethanes (“TPU”s), and to rubber in vulcanized rubberbelts. For some applications, bonding may be enhanced with suitableovercoat adhesives.

The general term “polyurethane” (PU) may be commonly used in the art toinclude polyureas, polyisocyanurates, and other polymers which may havelittle or no actual urethane groups or linkages. Herein, “polyurethane”is used in a more literal sense to refer to polymers which are reactionproducts of isocyanates and alcohols and thus contain significantamounts of urethane linkages, —NR—CO—O—. Herein and in the claims,“polyurea” is used to refer to polymers which are reaction products ofisocyanates with themselves in the presence of moisture or water, orreactions of isocyanates with amines which may be reactionintermediates, resulting in significant amounts of urea linkages,—NR′—CO—NR″—. In these urethane or urea linkages, R, R′, and R″ are eachindependently hydrogen; alkyl, or aryl groups. Included in the term“polyurea” are biurets, which are formed when a urea group reacts withadditional isocyanate to form a branched polymer. “Polyisocyanurate” isused to refer to polymers which are reaction products of isocyanateswith themselves at elevated temperatures to form a tri-isocyanurate ringstructure. The terms, polyurea and polyurethane, are not meant to implytotal purity of reaction, but are used to indicate what is believed tobe the dominant reaction mechanism and/or reaction product involved inthe inventive adhesive system. Thus, minor amounts of other reactionproducts or other reaction mechanisms may be involved without furthermention in what may still be referred to herein as a predominantlypolyurea-urethane reaction product. The term “polymer” will beunderstood to include polymers, copolymers (e.g., polymers formed usingtwo or more different monomers), oligomers and combinations thereof, aswell as polymers, oligomers, or copolymers that can be formed in amiscible blend. The term “pre-polymer” refers to a monomer or system ofmonomers that have been reacted to an intermediate molecular weightstate. This material is capable of further polymerization by reactivegroups to a fully cured high molecular weight state. As such, mixturesof reactive polymers with unreacted monomers may also be referred to aspre-polymers. Typically such prepolymers are polymers of relatively lowmolecular weight, usually between that of the monomer and the filmpolymer or resin. As such, one of skill in the art will appreciate thatmonomers react to form the polyurea-urethane such that the monomer is nolonger present once the polymer is formed. However, in some compositionsdescribed herein, both monomer and polymer may be present in theformulation prior to curing, and after curing, residual monomer mayremain in the cured polymer. The term “polyamine” is meant to refer tocompounds having at least two (primary and/or secondary) aminefunctional groups per molecule. The term “polyol” is meant to refer tocompounds having at least two hydroxyl functional groups per molecule.The term “diol” is meant to refer to compounds having two hydroxylfunctional groups per molecule. The term “triol” is meant to refer tocompounds having three hydroxyl functional groups per molecule. The term“polyisocyanate” and “polyisothiocyanate,” collectively referred to as“polyiso(thio)cyanate” are meant to refer to compounds having at leasttwo isocyanate or isothiocyanate, respectively, functional groups permolecule. The term “diisocyanate” is meant to refer to compounds havingtwo isocyanate functional groups per molecule.

The polyurethane prepolymers useful in embodiments of the invention maybe made by reacting a polyol with a polyisocyanate according to methodsknown in the art. Useful polyols include but are not limited topolyester polyols, polyether polyols, polythioether polyols,polycarbonate polyols, and polycaprolactone polyols. Polycaprolactonesmay be considered types of polyesters. Preferred polyols forapplications requiring thermal stability are nonoxidative up to 150® C.,and include but are not limited to polyester polyols, polycaprolactonepolyols, and polycarbonate polyols. The polyester polyols used in thepresent invention include but are not limited to reaction products ofpolyhydric alcohols, preferably dihydric alcohols with the addition ofsome trihydric alcohol, and/or polybasic carboxylic acids, preferablydibasic carboxylic acids with the addition of some tribasic carboxylicacids. The corresponding polycarboxylic acid anhydrides or correspondingpolycarboxylic acid esters of lower alcohols or mixtures thereof arepreferred over their free polycarboxylic acid counterparts for preparingthe polyesters. The polycarboxylic acids may be aliphatic,cycloaliphatic, and/or aromatic in nature. The following are mentionedas non-limiting examples: succinic acid, adipic acid, suberic acid,azelaic acid, sebasic acid, phthalic acid, isophthalic acid, trimelliticacid, phthalic acid anhydride, tetrahydrophthalic acid anhydride,hexahydrophthalic acid anhydride, tetrachlorophthalic acid anhydride,endomethylene tetrahydrophthalic acid anhydride, endomethylenetetrahydrophthalic acid anhydride, glutaric acid anhydride, fumaricacid, dimeric and trimeric fatty acids, optionally mixed with monomericfatty acids, dimethylterephthalate and terephthalic acid-bis-glycolesters. Suitable polyhydric alcohols used to produce such polyestersinclude but are not limited to the following; ethylene glycol, 1,2- and1,3-propylene glycol, 1,4- and 2,3-butylene glycol, 1,6-hexanediol,1,8-octanediol, 1,10-decanediol, neopentyl glycol, 1,4-cyclohexanedimethanol or 1,4-bis-hydroxymethylcyclohexane,2-methyl-1,3-propanediol, glycerol, trimethylopropane (“TMP”),1,2,6-hexanetriol, 1,2,4-butanetriol, trimethylolethane, and mixturesthereof. Polyesters of lactones, such as ε-caprolactone, andhydroxycarboxylic acids, such as omega-hydroxycaproic acid, may also beused.

Suitable polycarbonate polyols are known and may be prepared, forexample, by the reaction of diols, such as 1,3-propanediol,1,4-butanediol, 1,6-hexanediol, 1,10-decanediol, neopentyl glycol,diethylene glycol, triethylene glycol or tetraethylene glycol, andmixtures thereof, with diaryl carbonates, e.g. diphenyl carbonate,dialkyl carbonate, e.g. diethyl carbonate, or phosgene. Suitablepolyether polyols are known and include hydroxyl-terminated polyetherssuch as those based on alkylene oxides which includes propylene oxide(PPO), ethylene oxide, and polytetramethylene oxide (PTMO). Thepreferred alkylene oxide is a polypropylene oxide. The polyol may be apolyether polyol having an average hydroxyl functionality of from about2 to 8 with an average hydroxyl equivalent weight of from about500-5000, or a polyether polyol hydroxyl functionality of from about 2to 4 with an hydroxyl equivalent weight of approximately 1000-3000. Inan embodiment, the polyether polyol includes an average hydroxylfunctionality of from about 2-3 with an average hydroxyl equivalentweight of approximately 1500-2500.

Preferred polyols are polycarbonate polyols and polyester polyols withmolecular weights from about 500 to about 4000 or 5000, or mixtures ofthese polyols. The more preferred polyols are poly(hexamethylenecarbonate) (“PCB”) diol and/or triol, polycaprolactone (“PCL”) dioland/or triol, and poly(hexamethylene adipate) diol and/or triol withmolecular weights from about 300 or 500 to about 4000 or 5000. The mostpreferred polyols for tensile cords for belts and hose arepolycaprolactone diols and/or triols. The most preferred molecularweights for diols range from about 1500 to about 2500 and for triolsrange from about 1000 to about 4000, or from about 2500 to about 3500.The polyols are dried to a moisture level of less than about 0.03% byweight, and more preferably, to a level of about 0.0150% by weight priorto reaction with the diisocyanates to form the polyisocyanateprepolymers useful for this invention. The polyol used to prepare theprepolymer may be a mixture of at least one triol selected from theabove polyols and one or more other polyols, preferably diols. The mostpreferred diols and triols are the most preferred polyols listed above.The amount of triol crosslinker in the polyol mixture is notparticularly limited since it is possible to use anywhere from about 2%up to 100% triol. Nevertheless in preferred embodiments, the amount oftriol in the polyol mixture may preferably be from 5% up to about 65% byweight of the total polyol component of the prepolymer, more preferablyfrom about 15% to about 55%. The remainder of the polyol mixture may bediol. Too little triol leads to insufficient crosslinking and little orno improvement in high temperature performance, while too much triolleads to processing or mixing difficulties from the increase inviscosity of the prepolymer and/or lack of wetting or penetration oftextile reinforcement by the polyurethane and/or chemical instability ofthe mixture. In embodiments of the invention, the prepolymer may beprepared by mixing a diol-based prepolymer with a triol-basedprepolymer. However, the increased viscosity of triol-based prepolymersmakes this difficult. Thus, a preferred embodiment is a prepolymerprepared from a mixture of diol and triol, preferably PCL polyols.

Useful polyisocyanates for preparing the prepolymers include but are notlimited to para-phenylene diisocyanate (“PPDI”), 2,4- and/or 2,6-toluenediisocyanate (“TDI”), 4,4′-methylene diphenyl diisocyanate (“MDI”),hexamethylene diisocyanate (“HDI”), 1,5-naphthalene diisocyanate(“NDP”), trans-1,4-cyclohexane diisocyanate (“t-CHDI”), trimethylxylylene diisocyanate (“TMXDI”), isophorone diisocyanate (“IPDI”) andthe like, and mixtures thereof. The organic polyisocyanates suitable forthe polyisocyanate prepolymers used in the present invention arepreferably those possessing the following characteristics: compact andsymmetric structure for aromatic compounds, or trans or trans,transgeometric structure for aliphatic compounds, for improved phaseseparation of the resulting elastomers, and high reactivity with aminegroups or water to eliminate the need for catalysts in the formulations,which otherwise accelerate reversion of the resulting elastomers at hightemperatures. Polyisocyanates preferred as starting components for thepreparation of the polyurethane prepolymers include but are not limitedto compact, symmetric aromatic diisocyanates, including but not limitedto PPDI, NDI, and 2,6-toluene diisocyanate (“2,6-TDI”). Thepolyisocyanates useful as starting components for the preparation of thepolyisocyanate prepolymers also include cycloaliphatic diisocyanateswith trans or trans,trans geometric configuration. These isomers aregenerally pure, i.e., they exist in the substantial absence ofcis-configured isomers, and thus promote good phase separation oncecured. These include but are not limited to t-CHDI, andtrans,trans-4,4′-dicyclohexylmethyl diisocyanate (“t,t-HMDI”). Mostpreferred for use in embodiments of the present invention in reinforcingtensile cords for belts and hose is PPDI.

The chain extenders (i.e. curatives) useful in the present invention areselected so as to be capable of adequate reaction time with theprepolymer, and to give the desired urea linkages, with a desired amountof phase separation and hard segment properties. The chain extender mayinclude a compound of aliphatic amines, aromatic amines and mixturesthereof. The chain extender may include an aliphatic amine such asethylene diamine, 1,3-diaminopropane, 1,4-diaminobutane,hexamethylenediamine, aminoethanolamine, 1,4-diaminocyclohexane,isophorone diamine (“IPDA”) and triethylenetetramine. The chain extendermay preferably be an aromatic amine which may include2,4-diaminotoluene, 2,6-diaminotoluene, 1,5-napthalenediamine,1,4-phenylenediamine, 1,4-diaminobenzene, 4,4′-methylenebis(orthochloroaniline) (“MOCA”), 1,4-butylene glycol,4,4′-methylenebisdianiline (“MDA”), 3,5-diethyl-2,4-diaminotoluene,diethyl toluene diamine (“DETDA”), trimethyleneglycol diaminobenzoate(“TMGDAB”), 4,4′-methylenebis(3-chloro-2,6-diethylaniline) (“MCDEA”),and 3,3′,5,5′tetraisopropyl-4,4′-methylenebisaniline. Preferred chainextenders are small, compact and symmetric aromatic diamines. Preferablythe chain extender is no larger than TMGDAB. Preferably the curative hasno more than two phenyl rings and/or no longer than a three-carbonaliphatic group. In a more preferred embodiment, the chain extender iswater, including for example ambient moisture. Water forms the mostcompact of the urea linkages, —NH—CO—NH—. The simple urea linkagesformed by the reaction with water as the curative minimize the size ofthe hard segment domains, while still giving good phase separation andphysical properties. This leads to good flexibility of the resultingtreated fibers or tensile cords, as desired for use in dynamic rubberapplications like belts and hose. Moreover such a small hard segmentbased on water, in combination with a small symmetric diisocyanate, suchas PPDI, results in a good overall balance of properties includinghigh-temperature stability, flexibility, modulus and strength.

Symmetric primary diamine chain extenders useful in the preparation ofpolyurea-urethane adhesive in accordance with an embodiment of thepresent invention are those capable of reacting with polyisocyanateprepolymers rapidly without the need for catalysts. The symmetry of thechain extenders useful in an embodiment of the present inventionprovides improved phase separation and hence increase the thermalstability of the final PUU elastomers in dynamic applications. Suitableprimary diamine chain extenders include but are not limited to symmetricaromatic amines with molecular weights of from about 90 to about 500,and mixtures thereof. Examples include: 1,4-phenylenediamine,2,6-diaminotoluene, 1,5-naphthalenediamine, 4,4′-diaminodiphenylmethane, 3,3′-dimethyl-4,4′-diaminodiphenyl methane,1-methyl-3,5-bis(methylthio)-2,6-diaminobenzene,1-methyl-3,5-diethyl-2,6-diaminobenzene,4,4′-methylene-bis-(3-chloro-2,6-diethylaniline),4,4′-methylene-bis-(ortho-chloroaniline),4,4′-methylene-bis-(2,3-dichloroaniline), trimethylene glycoldi-para-aminobenzoate, 4,4′-methylene-bis-(2,6-diethylaniline),4,4′-methylene-bis-(2,6-diisopropylaniline),4,4′-methylene-bis-(2-methyl-6-isopropylaniline), 4,4′-diamino diphenylsulfone, and the like. The symmetric primary diamine chain extenders mayoptionally be combined with a small amount of secondary diamine chainextenders in order to vary elastomer characteristics such as hardness.Suitable examples of secondary diamine chain extenders have molecularweights of from about 150 to about 500, and include but are not limitedto N,N′-di-sec-butyl-amino benzene andN,N′-di-sec-butyl-amino-diphenylmethane.

It may be advantageous to block the isocyanate groups in the prepolymer.Suitable blocking reagents include polyketimines, phenols, caprolactam,oximes, triazoles, certain alcohols, and β-dicarbonyl compounds such asethyl acetoacetate and ethyl malonate. A preferred blocking agent ismethyl ethyl ketoxime (“MEKO”).

The present invention may also utilize various other additives in orderto assist in the processing of a product from the composition of theinvention or to assist in the functioning of a product made from theelastomer of the invention, including antioxidants, plasticizers,fillers, colorants, adhesion promoters, co-reactants, chain extenders,and the like. For example, antioxidants are particularly useful when theelastomeric composition of the present invention is utilized in a powertransmission belt product. Suitable antioxidants include2,6-di-t-butylphenol and polyalkylene glycol esters of hindered phenolsof substituted alkanoic acids. Examples of antioxidants include3,5-di-t-butyl-4-hydroxybenzoic acid ester of ethylene glycol,bis{3-(3-methyl-5-t-butyl-4-hydroxyphenyl) propionate} of trimethyleneglycol. Examples of useful or suitable plasticizers includeorgano-phosphates, dialkyl-ether di-alkylesters and polyalkylene-etherdi-alkylesters, such as di- or poly-ethylene glycol di-alkylesters.Dialkyl-ether diesters include C₄ to C₁₂-esters of C₁- to C₄-ether- orpolyether-dicarboxylic acids. Examples of such plasticizers may includeesters such as caprate, caprylate, hexanoate, heptanoate, pelargonate,2-ethylhexoate, and the like. Examples of such plasticizers may includedi-alkylesters of ethers such as ethylene glycol, propylene glycol,triethylene glycol, tetraethylene glycol, and polyethylene glycolshaving a molecular weight of up to about 800. Other polyols,polyisocyanates, isocyanate-terminated polymers, epoxies, and/or aminesmay be included, though preferably they are not included, as adhesionpromoters, co-reactants, chain extenders.

Other added compounds may be useful with the composition of the presentinvention. These include catalysts to decrease the reaction time of thecomponents. The catalysts may be selected from any desirable compoundknown in the art such as organo-metal compounds, tertiary amines, andalkali metal alkoxides. However, the polyurea-urethanes can be preparedwith or without catalysts, whereas polyurethanes based on polyols whichdo not contain amine terminated groups are most typically prepared witha catalyst. Suitable organo-metal compounds useful as catalysts includebut are not necessarily limited to aliphatic soaps of tin, mercury,iron, zinc, bismuth, antimony, cobalt, maganese, vanadium, copper andthe like. Examples include organic ligands which are carboxylic acids of2-20 carbons, such as dibutyl tin dilaurate, dimethyl tin dilaurate,phenylmercuric propionate, copper naphthenate, bismuth neodecanoate, andthe like. In a preferred embodiment, no catalyst is used.

Thus, a preferred embodiment of an adhesive composition according to theinvention comprises as the only reactive ingredients the polyurethaneprepolymer and a compact diamine curative or water alone as thecurative.

Throughout the present disclosure, the term “cord treatment” is used todenote a material applied to a yarn and/or yarn filament (which may ormay not include a sizing) and which ends up located at least on aportion of the yarn and/or yarn filament surface or sized surface andwithin at least a portion of one or more interstices formed between suchfilaments and yarns.

Many polyisocyanate prepolymers are commercially available and may bebeneficially employed in the practice of one or more embodiments of thepresent invention; and include those generally referred to as “low free”prepolymers as described for example in U.S. Pat. No. 6,174,984 toPeter, U.S. Pat. No. 5,703,193 to Rosenberg, U.S. Pat. Pub. No.2003/0065124 to Rosenberg et al., and U.S. Pat. No. 6,046,297 toRosenberg et al., in which the level of free diisocyanate in theprepolymer is reduced to a level of, e.g., less than 1% of theprepolymer, or less than 0.5%, or less than 0.25%, e.g., about 0.1% orlower.

Suitable isocyanate-terminated prepolymers for carrying out theinvention include the following available on the market. For example, anumber of useful prepolymers are available under one or more of theADIPRENE®, DURACAST, and VIBRATHANE® trademarks from ChemturaCorporation, including Adiprene® LFP 2950A, a preferredlow-free-monomer, PPDI-terminated polycaprolactone prepolymer; Adiprene®LFP 3940A, a PPDI-terminated polycarbonate prepolymer; Adiprene® LFP1950A, a PPDI-terminated polyester prepolymer; Adiprene® LF 1950A, aTDI-terminated polyester prepolymer, and Adiprene® LFP 950A, aPPDI-terminated polyether prepolymer; Adiprene® LF 1600D, LF 1700A, LF1800A, LF 1860A, and LF 1900A, are useful low-free-monomer,TDI-terminated polyester prepolymers; and Adiprene® LF 600D, LF 750D, LF753D, LF 800A, LF 900A, LF 950A, LFG 740D, LFG 920, and LFG 964A areuseful low-free-monomer, TDI-terminated polyether prepolymers; Adiprene®LFM 2450, Duracast™ C930, and Vibrathane® 8030 and 8045 are usefulMDI-terminated polycaprolactone prepolymers; Adiprene® LFH 120, 2840,and 3860 are useful HDI-terminated prepolymers. Useful prepolymers arealso available under one or more of the trademarks VULKOLLAN® andBAYTEC® from Bayer Material Science; under the TECHTHANE® trademark fromTrelleborg; under the AIRTHANE® and/or VERSATHANE® trademarks from AirProducts and Chemicals, Inc.; polyurethane prepolymers sold under theECHELON™ trademark from Dow; and so on.

Referring to FIG. 1, a typical timing belt 10 is illustrated. Belt 10includes elastomeric main body portion 12 and sheave contact portion 14positioned along the inner periphery of main body portion 12. Thisparticular sheave contact portion 14 is in the form of alternatingtransverse teeth 16 and land portions 18 which are designed to mesh witha transverse-grooved pulley or sprocket. Tensile layer 20 is positionedwithin main body portion 12 for providing support and strength to belt10. In the illustrated form, tensile layer 20 is in the form of aplurality of tensile cords 22 aligned longitudinally along the length ofmain body portion 12. It should be understood that, in general, any typeof tensile layer 20 known to the art may be utilized. Moreover, anydesired material may be used as the tensile member, such as cotton,rayon, polyamide, polyester, aramid, steel, glass, carbon, PBO,polyketone, basalt, boron, and even discontinuous fibers oriented forlow load carrying capability. In the embodiment of FIG. 1, tensile layer20 is in the form of illustrated tensile cords 22 made from one or moreyarns of high-modulus fiber, twisted or plied together into a cord andtreated with the PUU adhesive treatment described herein. Preferredhigh-modulus fibers include carbon, polyethylene naphthalate (PEN),poly(p-phenylene-2,6-benzobisoxazole) (PBO), aramid, basalt, boron, orliquid crystal polymer (LCP). In a preferred embodiment, the cords 22comprise aramid or carbon fiber. More preferably, the cord may be atwisted filament yarn, or a twisted bundle of yarns of continuous carbonfilaments.

By aramid is meant a long chain synthetic polyamide having its amidelinkages attached directly to two aromatic rings in either the para ormeta position. In the present invention, use may be made, for example,of PPD-T, poly(p-benzamide), copoly(p-phenylene/3,4′-oxydiphenyleneterephthalamide), or the like. By PPD-T is meant the homopolymerresulting from mole-for-mole polymerization of p-phenylene diamine andterephthaloyl chloride and, also, copolymers resulting fromincorporation of small amounts of other diamines with the p-phenylenediamine and of small amounts of other diacid chlorides with theterephthaloyl chloride. Commercial aramid fibers suitable for thepractice of this invention include those sold under the trademarksTEHINCONEX, TECHNORA, and TWARON by Teijin Limited, and under thetrademarks NOMEX, and KEVLAR by E.I. DuPont de Nemours and Company.

Reinforcing fabric 24 may be utilized and intimately fits along thealternating teeth 16 and alternating land portions 18 of belt 10 to forma face cover or tooth cover for the sheave contact portion. This fabricmay be of any desired configuration such as a conventional weaveconsisting of warp and weft threads at any desired angle or may consistof warp threads held together by space pick cords, or of a knitted orbraided configuration, or a nonwoven fabric, and the like. More than oneply of fabric may be employed, or combinations of different fabrictypes. If desired, fabric 24 may be cut on a bias so that the strandsform an angle with the direction of travel of the belt. Conventionalfabrics may be employed using such materials as cotton, polyester,polyamide, acrylic, aramid, polyketone, hemp, jute, fiberglass, andvarious other natural and synthetic fibers including blends orcombinations thereof. In a preferred embodiment of the invention, fabriclayer 24 consists of an expansible wear-resistant fabric in which atleast one of the warp or weft threads is made of nylon. In the preferredform, fabric layer 24 is made from a nylon 66 stretch fabric, andpresents an elastomer-free (polyurethane/urea-free) surface for engagingcooperating drive sheaves. The elastomer-free surface may include apolymeric film laminated to the fabric. The fabric may also be treatedwith the inventive PUU cord adhesive if desired.

Referring to FIG. 2, standard notched V-belt 26 is illustrated therein.V-belt 26 includes an elastomeric body portion 12 similar to that ofFIG. 1 and tensile reinforcement layer 20 in the form of cords 22, alsosimilar to that as illustrated in FIG. 1. The elastomeric body 12,tensile layer 20, and cords 22 of V-belt 26 may be constructed from thesame materials as described above for FIG. 1. It should be noted thatthe tensile layer 20 may optionally include an elastomeric compositionor rubber material that is different than the rest of the main bodyportion in order to provide a transitional layer in terms of modulus orother property and/or to function as an adhesive layer between cord andmain body. The optional adhesive rubber member may for example be ofhigher modulus than the main body as described in U.S. Pat. No.6,616,558 to South, the contents of which are hereby incorporated hereinby reference.

V-belt 26 also includes sheave contact portion 14 as in the powertransmission belt of FIG. 1. In this embodiment, however, sheave contactportions 14 are the two juxtaposed sides of the belt, designed to wedgeinto a V-sheave. The bottom surface of V-belt 26 is in the form ofalternating notch depression surfaces or troughs 28 and projections 30.These alternating notched depression surfaces 28 and projections 30 mayfollow a generally sinusoidal path as illustrated which serves todistribute and minimize bending stresses as the sheave contact portion14 passes around pulleys and sheaves. Various notch profiles thatdeviate from sinusoidal in various ways are also useful. However,troughs 28 and projections 30 are optional. Included in the category ofV-belts are those V-belts designed for continuously variabletransmission (“CVT”) applications, which often exhibit a belt bodyrelatively wider than the belt thickness.

Referring to FIG. 3, multi-V-ribbed belt 32 is illustrated.Multi-V-ribbed belt 32 includes main elastomeric body portion 12 as inthe belts of FIGS. 1 and 2 and also includes tensile reinforcementmember 20 preferably in the form of cords 22, also as previouslydescribed. Longitudinally grooved sheave contact portion 14 is in theform of a plurality of raised areas or apexes 36 alternating with aplurality of trough areas 38 having oppositely facing sides which definedriving surfaces 34 of the belt 32. In each of these instances of FIGS.1-3, sheave contact portion 14 is integral with main body portion 12 andmay be formed from the same elastomeric material to be described ingreater detail below, or layered of different material. While thepresent invention is illustrated with reference to the embodiments shownin FIGS. 1-3, it should be understood that the present invention is notto be limited to these particular embodiments or forms as illustratedbut rather is applicable to any belt construction within the scope ofthe claims as defined below.

Carbon fiber is typically made by carbonizing another fiber such aspolyacrylonitrile fiber, wherein during the carbonizing process thediameter of the fiber is substantially reduced. Carbon yarn is generallycharacterized by the number of fibers contained therein rather than bydenier or dtex. A nomenclature of numbers and the letter “k” are used todenote the number of carbon fibers in a yarn. Of course, carbon fibermay be characterized by such other terms where desired. In a “3 k”carbon fiber yarn, the “k” is an abbreviated designation for “1000fibers,” and the “3” designates a multiplier. Thus “3 k” carbon yarnidentifies a yarn of 3000 fibers or filaments. The filaments aregenerally of sufficient length to be considered continuous. Like othertextile materials, a number of carbon fibers are combined to form ayarn. A yarn may be combined with other yarn to form a larger yarn, andthe yarn or yarn bundles may be twisted together to form a cord. Carbonfiber may have an extremely small diameter which may be in the range offrom about 4 to about 8 microns, or about 5 to 7 microns. Individualfibers are easily fractured when a yarn is processed to form a cord. Forthis reason, it is desirable to minimize the number of mechanicaloperations that the yarn is subject to when forming a cord. For example,twisting several yarns together to form a yarn bundle and reversetwisting the so plied yarn bundles to form a cord are mechanicaloperations that fracture individual fibers. The number of fractures arelessened by reducing the number of twisting operations. To form adesired cord size may include bundling together multiple yarns ofsmaller filament count, for example, five 3 k yarns to obtain 15 k(designated 3 k−5), or three 6 k yarns to obtain 18 k cord (designated 6k−3). Preferably the twist level is not too high so as not to damagefibers. Thus a preferred twist level is from 0.75 to 2.5 turns per inch,or up to about 2 turns per inch. The final carbon fiber bundle may befrom 3 k to 60 k, depending on the desired application.

Fiber manufacturers often coat fibers with a sizing which acts tolubricate the fiber and inhibit fracturing as the fiber is processedinto yarns and wound on spools. In some instances, the sizing may have achemical structure that is compatible with an adhesive used to treat acord for inclusion into a power transmission belt. Types of sizing usedby carbon fiber manufacturers include for example epoxies, blends ofepoxy with polyurethane, organosiloxanes, polyamide-imides, and others.Sizing may be present at a pickup weight of about 0.1 to about 2.5%based on the yarn final weight. It is believed that embodiments of theinvention described herein are not particularly sensitive to the type orlevel of sizing which may be present on the carbon fiber. It may be thatthe primary mode of bonding of the PUU adhesive treatment to the carbonfiber bundle is physical interlocking rather than chemical bonding.Also, the present invention may involve using a solvent to apply the PUUadhesive to the carbon fiber bundle, and the solvent may penetrate oreven remove the sizing if desired.

The elastomeric belt (or other article's) body portion may be vulcanizedrubber or other crosslinked elastomer such as cast polyurethane (PU); ormay be thermoplastic elastomer (TPE) or thermoplastic polyurethane(TPU). The PUU cord treatment disclosed herein is particularlycompatible with a cast polyurethane or PUU belt body, and canadvantageously be used therewith without need for any additionaladhesive treatment. Likewise, the PUU cord treatment may be compatiblewith TPE and TPU elastomers and may not require any additional adhesivetreatment for use therewith. In the case of vulcanized rubber articles,it may be advantageous to include one or more additional adhesivetreatments to provide improved bonding between the PUU-treated tensilecord and the vulcanized elastomer. Such an additional adhesive treatmentwill be referred to herein as an overcoat or an overcoat adhesive. Itmay be advantageous to use two different overcoat adhesives to providemaximum bonding between the PUU and a rubber belt body material.

Regarding the main elastomeric body for use with an embodiment of thePUU-treated tensile cord, useful cast PU or PUU compositions that may beutilized in the practice of various embodiments of the presentinvention, and such compositions and methods are described for examplein U.S. Pat. No. 5,231,159 to Patterson et al. and U.S. Pat. No.6,964,626 to Wu et al., the contents of which are incorporated herein byreference. PUU typically has better dynamic properties relative to PUdue to enhanced phase separation, tougher hard segments, etc., and PUUis therefore preferred for high-performance belt applications.

The elastomeric body may be formed of TPE or TPU using for examplethermoplastic lamination processes for long length belting, or suitableother molding processes. TPE types that may be useful in variousembodiments include without limit polystyrene-elastomer blockcopolymers, polyester block copolymers, polyurethane block copolymers,polyamide block copolymers and polypropylene/EP copolymer blends. TPUtypes that may be useful in various embodiments are not particularlylimited, but may include similar chemistry as discussed above inconnection with cast polyurethanes, such as polyester thermoplasticurethanes or polyether thermoplastic urethanes. Thermoplastic beltingembodiments may have the general form of the toothed belt of FIG. 1,e.g. an endless belt, either as molded or by joining two belt endstogether. Embodiments may have two ends which may be clamped to variousassociated mechanisms, for example, in conveying, transporting, holding,or positioning applications.

In each of the cases of FIGS. 1-3 shown above, the main belt bodyportion 12 may be formed of any conventional and/or suitable curedelastomer composition, and may be of the same as or different from thatdescribed below in relation to the optional adhesive rubber membercomprising tensile layer 20. Suitable elastomers that may be utilizedfor this purpose include for example polyurethane elastomers (includingas well polyurethane/urea elastomers and so-called millable gums) (PU),polychloroprene rubber (CR), acrylonitrile butadiene rubber (NBR),hydrogenated NBR (HNBR), styrene-butadiene rubber (SBR), alkylatedchlorosulfonated polyethylene (ACSM), polyepichlorohydrin, polybutadienerubber (BR), natural rubber (NR), and ethylene alpha olefin elastomerssuch as ethylene propylene copolymers (EPM), ethylene propylene dieneterpolymers (EPDM), ethylene octene copolymers (EOM), ethylene butenecopolymers (EBM), ethylene octene terpolymers (EODM); and ethylenebutene terpolymers (EBDM); ethylene vinylacetate elastomers (EVM);ethylene methylacrylate (EAM); and silicone rubber, or a combination ofany two or more of the foregoing.

To form the elastomeric belt (or other article's) body portion 12 inaccordance with an embodiment of the present invention, the elastomer(s)may be blended with conventional rubber compounding ingredientsincluding fillers, plasticizers, stabilizers, vulcanizationagents/curatives and accelerators, in amounts conventionally employed.For example, for use with ethylene-alpha-olefin elastomer and dieneelastomers such as HNBR, one or more metal salts of alpha-beta organicacids may be employed in amounts now conventionally utilized to improvedynamic performance of the resultant article. Thus zinc dimethacrylateand/or zinc diacrylate may be utilized in such compositions in amountsof from about 1 to about 50 phr; or alternatively of from about 5 toabout 30 phr; or of from about 10 to about 25 phr. These materialsfurthermore contribute to the adhesiveness of the composition, andincrease the overall cross-link density of the polymer upon curing withperoxide or related agents through ionic crosslinking, as is now wellknown in the art.

One skilled in the relevant art would readily appreciate any number ofsuitable compositions for utilization in or as the elastomeric portionsof the rubber articles useful herein. A number of suitable elastomercompositions are described for example in The R. T. Vanderbilt RubberHandbook (13^(th) ed., 1996), and with respect to EPM or EPDMcompositions and such compositions having particular high tensilemodulus properties, are furthermore set forth in U.S. Pat. Nos.5,610,217, and 6,616,558 respectively, the contents of which, withrespect to various elastomer compositions that may be suitable for usein the formation of power transmission belt body portions, arespecifically incorporated herein by reference. In an embodiment of thepresent invention associated with automotive accessory driveapplications, the elastomeric belt body portions 12 may be formed of asuitable ethylene alpha olefin composition, such as an EPM, EPDM, EBM orEOM composition.

The elastomeric main belt body portion 12 may moreover be loaded withdiscontinuous fibers as is well known in the art, utilizing materialssuch as including but not limited to cotton, polyester, fiberglass,aramid and nylon, in such forms as staple- or chopped fibers, flock orpulp, in amounts generally employed. In a preferred embodiment relatingto profiled (e.g., as by cutting or grinding) multi-v-ribbed belts, suchfiber loading is preferably formed and arranged such that a substantialportion of the fibers are formed and arranged to lay in a directiongenerally transverse the direction of travel of the belt. In moldedmulti-v-ribbed belts and/or synchronous belts made according to flowthrough methods however, the fiber loading would generally lack the samedegree of orientation.

For use in rubber belts, the PUU-treated cords of the present inventionmay advantageously be coated with a secondary adhesive intended toprimarily coat the outer surface of the cord bundle. Such an adhesive iscalled an overcoat adhesive herein. Overcoat is generally applied at alevel in the range of from about 1% to about 10% dry weight, based onthe final weight of the so treated cord. Examples of useful overcoatadhesives are found in the art and include without limitation variouscompositions sold under the trademarks CHEMLOK or CHEMOSIL by LordCorporation, and various compositions sold under the trademark CILBONDby Chemical Innovations Limited (CM). The particular overcoat may bechosen to be compatible with both the underlying adhesive treatment andthe rubber belt body and to have other desired properties such as heatresistance, environmental resistance, or the like. It may beadvantageous to apply two separate overcoat adhesive compositions. Ifthe PUU-treated cord is only partially impregnated, a first overcoat maybe used to fully impregnate the cord and a second overcoat to coat theouter surface of the treated cord bundle. For some combinations of PUUtreated cord and a rubber belt body composition, it may be advantageousto use a two-layer overcoat to ensure good bonding, for example, sincePUU may be more polar than many elastomers.

Thus, the invention provides a method for preparing a high-modulustensile cord, such as carbon cord, at least partially filled orimpregnated with a PUU binder. Compared to prior art use of greigecarbon cord (or other high-modulus cords) in cast PU belts, theinvention provides independent control of the cord properties. Forexample, the PUU binder used in a carbon cord may be selected to besofter than the cast PU of the belt body. The invention thus may improvebelt handling properties without negatively impacting dynamic load orflex capacity. The invention may also improve the processing and theproduct produced in low pressure casting operations and in processes inwhich the casting resin has a faster gel time or higher viscosity,because the cord is already impregnated with a PUU binder, which givethe cord integrity and prevents fraying upon cutting, whether or not thesubsequent casting resin penetrates the cord also. The ability to treatthe already-twisted carbon fiber with a low viscosity adhesiveadvantageously may produce a generally rounder, more uniform cord thanprior treating methods which required spreading the fibers duringtreating, followed by twisting.

In one embodiment of a cast PU article or belt having a high modulustooth or body PU compound, the tensile cord may be treated with asolution of polyurethane prepolymer and cured with a smaller curativemolecule than the cast PU, yielding a lower modulus binder of similar,or at least compatible chemistry. Thus, the complex modulus of the cordmay be reduced (i.e. the flexibility of the cord may be increased)without negatively affecting composite integrity. There is good adhesionbetween the filled cord and the body/tooth compound. Preferably the bodyPU compound is replaced within the cord with a similar prepolymer butwith a smaller, more compact hard segment or curative such as water, inorder to give a softer, lower modulus cord treatment. Thus, the cordadhesive curative may preferably be water, while the body of the articlemay utilize the same prepolymer but a more conventional chain extendersuch as diamine or polymeric diamine or the like.

To apply the PUU adhesive resin to the tensile cord fibers, the adhesivecomposition ingredients may be dissolved or suspended in a suitablesolvent. A suitable solvent is one that will dissolve the prepolymer andalso wet out the fibers of the tensile cord for good impregnation. A lowcontact angle between the solvent or adhesive solution and the fiber isdesirable. Suitable solvents include without limitation, tetrahydrofuran(“THF”), dimethyl sulfoxide, dimethyl formamide, N-methylpyrrolidone(“NMP”), toluene, xylene, benzene, acetone, methyl ethyl ketone, methylisobutyl ketone, and the like. For treating carbon fiber cords accordingto an embodiment of the invention, preferable solvents include THF andtoluene.

In a preferred embodiment, a low free PPDI/polycaprolactone prepolymeris dissolved in a solvent, such as toluene or THF, at a predeterminedconcentration which may be in the range 10-50% by weight, or from 20% to40% by weight, and the solution is added to a dip tank. The cord, whichmay preferably be in twisted form, e.g. from 0.75 to 2.5 turns per inchfor carbon fiber cord, is pulled though the dip tank and then through anoven, where, the solvent is flashed off. Alternately, the cord may bedipped and dried in untwisted form, with means to spread the fibers formaximum penetration, followed by twisting. After passing through theoven, and removing most of the solvent, the prepolymer is allowed toreact with water. The cord can be dipped in a water bath to enhance thereaction before spooling, for example to prevent sticking of the cord onthe spool. The water bath can, but need not, contain a chemical, such asa catalyst, that accelerates the formation of a urea skin on the outsideof the cord. Likewise heat, for example in a drying oven, can be used toaccelerate urea skin formation. The prepolymer on the inside of the cordwill cure with ambient environmental moisture. This cure on the insideof the cord may take several days, but the cord may be used in a productmade with cast PU at any time after treating, whether fully cured ornot. The cord will continue to cure as the product is cured. Even afully cured cord treatment will generally have sufficient reactivegroups to continue to cure and bond with the body material of a productduring product cure. Water performs the function of curative by reactingwith isocyanate groups on the prepolymer. Isocyanate reacts with waterto form carbamic acid. Carbamic acid dissociates to form an amine andcarbon dioxide. The amine will react with isocyanate to form adi-substituted urea linkage and further the condensation reaction. Thisreaction creates a very compact hard segment with urea linkages.

According to an embodiment of the invention, the PUU treatment mayadvantageously be 20-40% solids and preferably of low enough viscosityto fully penetrate the fiber bundle during a dip treatment whethertwisted or not. After the solvent is removed by drying, the PUUpreferably coats the individual fibers of the bundle, but need notcompletely fill the interstices of the cord. It may be advantageous forthe PUU resin to occupy from about 20% to about 99% or 100% of theinterstices, depending on the intended use of the treated cord. Inparticular, for use in cast polyurethane articles such as powertransmission belts, only partially filling the interstices, e.g., from20% to 90%, or 30% to 80% full, or 40% to 60% full, may leaveinterstices or voids that can be penetrated by the cast PU of the beltbody, thus providing a level of mechanical adhesion without making thecord overly stiff and still benefitting from the use of the PUUtreatment. When a cast PU belt body thus penetrates voids in thePUU-treated cord, the PU and PUU materials may be in intimate contact,facilitating chemical bonding between them. On the other hand, when thecord is to be overcoated with additional adhesives for chemical adhesionas might be done for bonding in certain rubber articles, more fullyimpregnated cord may be more suitable, e.g., from 40% to 100%, or 60% to99% full. The pickup levels, indicated for example as weight % adhesivepickup based on weight of the treated cord, may vary depending on thedegree of voids or interstices in the twisted cord. The pick up level ofthe PUU adhesive on the cord may be in the range from 6% to 25%, or 8%to 22% or from 10% to 15%.

Cast urethane belts according to an embodiment utilizing the inventivetensile cords may be made according to known methods such as thosedescribed in references already incorporated herein by reference.Likewise, TPE or TPU belts may be made by known methods, includingcontinuous lamination methods that produce belts having two ends,instead of endless belts. The two ends may be joined according to knownmethods to make endless TPE or TPU belts. Rubber belts may be built on amandrel, cured, and cut to width according to methods known in the art.

It should be understood that reinforcing cords according to anembodiment of the invention may be used in various kinds of elastomericcomposite articles, such as power transmission belts, transport ortransfer belts, straps, tires, hose, air springs, vibration mounts, etc.

Examples

The following illustrations and examples are not meant to limit theinvention, but demonstrate its usefulness in various embodiments.Examples demonstrate use of the invention in cast polyurea-urethane beltapplications, TPU belt applications, and rubber belt applications.

Illustration I.

A pair of 12 k−1 yarns identified as G30 700 12 k HTA-7C from Toho weretwisted in opposite directions to a level of 2.0±0.1 turns per inch toform “S” and “Z” 12 k carbon cords. A portion of the greige, twistedcord was used to make a slab of cast PU toothed belts of 8-mm pitchaccording to the method of U.S. Pat. No. 5,807,194 to Knutson et al.,referred to herein as Comparative Example 1 (“Comp. Ex.” 1). Anotherportion of the cord was treated according to an embodiment of thepresent invention and then used to make a second slab of inventive8-mm-pitch, toothed belts, referred to herein as Example 2 (“Ex.” 2).

For the PUU adhesive treatment of Ex. 2, a blend of di- andtri-functional PPDI-terminated polycaprolactone prepolymer with a finalfunctionality of approximately 2.1 was added to toluene solvent to makea 33 weight-percent solids solution for the dip tank. The greige twistedcord was dipped and then the solvent flashed off by passing the wet cordthrough an oven. Immediately after exit from the oven the cord wasdipped in a water bath, air dried, and then wound onto a spool. Solidspickup was determined for “S” and “Z” dipped cords at 16.1 and 14.0weight percent, respectively. Cord stiffness was measured immediatelyafter spooling and after sitting in a high humidity environmentovernight. Cord stiffness was measured on a Tinius Olsen StiffnessTester according to the procedure of ASTM D747 but based on the actualpeak bending force in units of pounds force (or kilograms force) forfive parallel cords tested at a 12.7-mm span over a deflection range offrom zero to 65°. The initial stiffness of Ex. 2 was 0.49 and 0.73 lbf,respectively. After sitting overnight the stiffness was measured at 1.14and 1.08 lbf, respectively. Water cure may be relatively slow, resultingin a gradual change in stiffness over hours or even days. Based on thereported equivalent cross section of carbon in the yarn (0.00455 cm²)and the final cord cross sectional area in the belts (0.00665 cm²), thevoid volume in the cord was calculated to be about 31.6% of the finalcross section. The weight percent of treatment picked up for the S and Zcords thus corresponds to the interstices of the cord being filled about55 to 60 percent with PUU resin. Inspection of the resulting cordsshowed that the outer layer of fibers was lightly coated leaving plentyof interstitial space for additional impregnation by the cast PU duringbelt building, resulting in very good adhesion of the cord to the beltbody. Tensile testing of the treated cord versus the greige cord yieldeda tensile strength of 148 lbs for the greige cord and 222 lbs for thetreated cord, a 50% improvement. This dramatic improvement in tensilestrength may reflect the difficulties in tensile testing greige yarns,and the improvement in handling properties of the treated yarn.Inspection of belt cross sections under high magnification revealed thatthe cast PU resin had substantially fully filled all intersticesremaining after adhesive treating the cord. The cast PU resinformulation used to make the belts was based on a TDI-terminatedpolyether prepolymer based on polytetramethylene ether glycol (“PTMEG”),cured with TMGDAB.

After belt manufacture, samples of cord were removed from greige- andtreated-cord belts and subjected to the cord stiffness test. Twoparallel cord samples were used instead of the usual five. The cord fromComp. Ex. 1 was stiffer than the treated cord, from Ex. 2, namely 0.66vs 0.52 lbf, respectively. The inventive cord treatment thus lowered thestatic bending stiffness of the cord in the belt by approximately 20%.

Dynamic belt bending testing at two frequencies and temperatures alsoshowed a significant modulus difference between greige and treatedcords. The results for this testing are presented in Table 1. At alltest conditions, belt bending moduli were lower for the belt withtreated cord of Ex. 2 than for the belt with greige cord of Comp. Ex. 1.Treatment of the cord with the inventive PUU adhesive treatment reducedthe dynamic bending modulus of the cord.

TABLE 1 Comp. Ratio of Ex. 2:Comp. 3-point dynamic bending test Ex. 1Ex. 2 Ex. 1 K* at 23° C., 0.1 Hz (N/mm)¹ 7.86 5.00 0.64 K′ at 23° C.,0.1 Hz (N/mm)² 7.59 4.88 0.64 K″ at 23° C., 0.1 Hz (N/mm)³ 2.03 1.090.53 K* at 100° C., 0.1 Hz (N/mm) 5.96 3.65 0.61 K′ at 100° C., 0.1 Hz(N/mm) 5.87 3.62 0.62 K″ at 100° C., 0.1 Hz (N/mm) 1.02 0.49 0.48 K* at23° C., 1.0 Hz (N/mm) 8.40 5.14 0.61 K′ at 23° C., 1.0 Hz (N/mm) 8.135.05 0.62 K″ at 23° C., 1.0 Hz (N/mm) 2.12 0.97 0.46 K* at 100° C., 1.0Hz (N/mm) 5.91 3.71 0.63 K′ at 100° C., 1.0 Hz (N/mm) 5.84 3.68 0.63 K″at 100° C., 1.0 Hz (N/mm) 0.93 0.46 0.49 ¹K* is the complex stiffness.²K′ is the storage or elastic stiffness. ³K″ is the loss or inelasticstiffness.

The PUU treatment of Ex. 2 was also mixed into THF at a concentration of25% solids by weight and used to cast a film on an IR window. Theresulting PUU film was 0.018 inches thick. It was placed in FTIRinstrument to follow the solvent evaporation and the reaction of the NCOgroups with water. The NCO peak area was reduced 50% after about 200minutes, and substantially gone after about 500 minutes. An attempt wasmade to cast a thicker film of the inventive treatment and the cast PUUof the belt body for tensile testing. Though some bubbles were observed,the resulting films were deemed sufficient for a tensile testcomparison. The water-cured adhesive treatment exhibited a modulus about⅔ less than that of the TMGDAB-cured belt material, an elongation aboutthe same, and a tensile strength about ⅓ less. Thus, according to anembodiment of the invention, a reinforcing cord may be treated with amoisture-cured PUU analog of a diamine-cured PUU casting composition toobtain a relatively lower modulus, more flexible cord with equivalent tomuch better tensile strength, and with excellent compatibility with thecast PUU.

The belts of Ex. 2 were subjected to a number of tests, demonstratingcertain advantages over Comp. Ex. 1. Belt tensile strength was measuredby mounting a belt on two 60-groove sprockets, and pulling on aconventional tensile test machine at 25.4 mm/min with a clip-onextensometer optional. Flex Conditioning of the belts was carried out ona two-point layout with two 22-groove pulleys driven at 3600 rpm with165-pound deadweight tension for 168 and 336 hours. Retained tensilestrength after (i.e., “post”) flex conditioning is reported in Table 2.In a back-bending test, belts were back-bent three times in the samelocation of the belt around a pipe of given diameter and then tensiletested with the damage location in the span between the two pulleys. Theretained tensile strength after back bending is also reported in Table2. Static cord adhesion tests (pulling a short length of two cords outof the belt) and a static tooth shear test on the belts showed nosignificant differences between Comp. Ex. 2 and Ex. 1. Finally, dynamicbelt tests were run on a dynamometer rig (“Dyno Testing”) to evaluatebelt load capacity, dynamic adhesion, durability and the like. DynoTesting used an 18-mm wide, 140-tooth, 8-mm GT® profile belt run at 19hp and 2000 rpm, on two 24-groove pulleys with 213 pounds dead weighttension at room temperature. Two different testers known forsignificantly different results were used. Two belt lives were averagedfor each result reported in Table 2.

It can be seen from Table 2 that the inventive belt has slightly highertensile strength initially and after flex conditioning than the controlbelt. This may be attributable to the treated cord having improvedhandling tolerance over the greige cord. However, the back-bending testshows most clearly a dramatic advantage of the softer PUU-treated cordover the greige cord. While the greige cord loses half its strengthafter the 27-mm back bends, the inventive cord suffers no strength loss.At tighter back bends, the inventive cord does lose strength, but at amuch lesser rate than the control belt. Thus, the inventive beltperforms similarly under 10-mm bends as the control under 27-mm bends.It can also be seen from Table 2 that the Ex. 2 belts performed a littlebetter on average than the control belts on the Dyno Testing (the toothshear failure mode was observed for all belts). Thus, the soft PUUadhesive treatment provides significant improvement in handlingtolerance without loss of other performance features such as adhesion orload capacity.

TABLE 2 Comp. Ex. 1 Ex. 2 Belt Tensile Strength Tests (lbf/inch beltwidth) Initial Tensile Strength 9406 11552 Post Flex Conditioning (168hrs.) 9500 10000 Post Flex Conditioning (336 hrs.) 9400 10000 After backbends at 27-mm diameter 4800 10900 After back bends at 17-mm diameter2600 7000 After back bends at 10-mm diameter 2000 4600 After back bendsat 4.5-mm diameter 1700 3700 Dyno Testing On Tester #1 (average life inhours) 316 379 On Tester #2 (average life in hours) 43.4 68.4

Illustration II.

In a second test series, belt Comp. Ex. 3 and Ex. 4 were constructedwith a polyester-based TPU belt body and woven nylon fabric on the toothsurface. These toothed belts were endless with a metric T10 profile (10mm pitch, and trapezoidal tooth shape) and cut to a width of 25 mm.Comp. Ex. 3 was constructed with a conventional steel cord, and Ex. 4used the same inventive cord of Ex. 2 above. Specimens of these twobelts were subjected to a cord adhesion test, the results of which areshown in Table 3. Table 3 shows that the inventive treated cord in Ex. 4has equal or better adhesive performance than the conventional cord usedin Comp. Ex. 3, demonstrating that an embodiment of the invention issuitable for use in TPU belts.

TABLE 3 Comp. Ex. 3 Ex. 4 Cord adhesion (N) 977.1 1060.4 Failure modeCord Adhesive break

Illustration III.

For this series, Torayca T700GC 41E 12 k−1 yarns were used to make 8-mmpitch toothed, cast PUU belts as in Illustration I. Control belts madewith greige, twisted cord are referred to as Comp. Ex. 5. A portion ofthe cord was treated according to another embodiment of the presentinvention and then used to make a slab of inventive 8-mm pitch toothedbelts, referred to herein as Ex. 6. The PUU adhesive treatment of Ex. 6comprised a polyester/TDI prepolymer, with a MEKO blocking agent on theisocyanate groups. The curative was the diamine, DETDA. The liquidmixture of blocked prepolymer and curative was impregnated into thecarbon fiber bundle under pressure, though use of a solvent as describedabove would have been easier. The belts were again evaluated for tensiledecay on the Flex Conditioning test, but at 150 pounds dead weighttension, and for handling damage by both back-bending and forwardbending on pipes of various diameters. The results are shown in Table 4.It can be seen that this embodiment also exhibits improved handlingresistance over the control. In another example of using a blockedprepolymer, designated Ex. 7, the curative was the diamine, MCDEA, butno belt data is available.

TABLE 4 Belt Tensile Strength Tests Comp. (lbf/inch belt width) Ex. 5Ex. 6 Initial Tensile Strength 12100 10100 Post Flex Conditioning (2hrs.) 8800 10100 Post Flex Conditioning (24 hrs.) 8600 10200 Post FlexConditioning (48 hrs.) 8000 10200 Post Flex Conditioning (190 hrs.) 80009900 After back bends at 50-mm diameter 5800 10300 After front bends at37-mm diameter 5500 10600

Illustration IV.

In this set of examples, an embodiment using PUU-treated carbon cord iscompared to a conventional RFL-treated carbon cord in a rubber, toothedbelt. A 12 k−1 carbon bundle was again PUU treated as in Ex. 2 ofIllustration I, but in addition, the treated cord was dipped in aCilbond 81 overcoat adhesive and dried again. For a control, anX-HNBR-RFL treated 12 k cord was prepared according to the methods ofU.S. Pat. No. 6,695,733 (see Table 1 therein and associated text, whichis hereby incorporated herein by reference), and also overcoated withCilbond 81. Toothed belts were made according to well-known methods,including applying a nylon fabric sleeve to a 97-groove (9.525-mm pitch)mandrel, helically winding both S and Z twisted cords at 18 totalstrands per inch giving suitable spacing to allow rubber to flowthrough, applying a layer of sulfur-cured HNBR rubber, and curing underpressure and temperature so that the rubber flows through the cord,presses the fabric into the grooves and forms the teeth, as thecomposite is cured. After removal of the resulting sleeve from themandrel, individual belts were cut to 19 mm width. The control beltswith RFL-treated cord are designated Comp. Ex. 8, and the inventivebelts with PUU-treated cord are designated Ex. 9. A number of belt testswere conducted and the results are shown in Table 5. The tensilestrength was measured as previously described, as was cord adhesion. Thejacket adhesion test involved peeling the tooth fabric off the belt,giving a minimum in the web region where jacket-cord adhesion isprimarily measured and a maximum in the tooth region where jacket-rubberadhesion is primarily measured. The belt running temperature wasmeasured over a 24 hour period on a no-load Flex Test rig. The Flex Testis illustrated in FIG. 4. A 97-tooth synchronous belt was run on adriving pulley 50 with 19 grooves, two driven pulleys 52 and 54, with 19grooves and 20 grooves respectively, two backside idlers 56 (50-mmdiameter) and a tensioner 58. A tension of 200 N was applied withtensioner 58 by a hanging weight. The Flex Test ran at 6200 rpm at roomtemperature.

Table 5 shows that the rubber belts according to the invention performcomparably to the control belts. It was noted that in some cases, theoriginal inventive belts tested inferior to the control, while the airaged inventive belts were comparable, e.g., on the cord adhesion testand the dynamic tooth durability test. This is believed due to the slowcure of the PUU material and indicates a possible advantageous use of apost-cure treatment or addition of a catalyst to the adhesive, for someembodiments of the invention. On the Flex Test rig, the inventivePUU-treated cord resulted in lower belt running temperatures thanRFL-treated cord, which is believed attributable to improved dynamicproperties of PUU over RFL.

TABLE 5 Comp. Ex. 8 Ex. 9 Original Air Aged Original Air Aged TensileStrength 43 44.5 31.5 32.5 (kN/20 mm) Cord Adhesion (N) 1050 1200 6501050 Jacket-Cord (Web) 28 26 26.5 25 Adhesion (N) Jacket-Tooth Adhesion140 110 100 110 (N) Belt Running 112 108 — 102 Temperature (° C.)Dynamic tooth 3000 10000 300 100,000 durability (cycles)

Illustration V.

This series of examples is largely a repeat of Illustration I, but with27.5% solids in the adhesive solution, variations in adhesive pickuplevels, and with a variety of other carbon cord sizes, including a muchlarger, 12 k−4 carbon cord bundle twisted 1.2-1.3 turns per inch. Awater dip after treatment was not used. As before, a portion of thegreige, twisted cords (both S and Z) were used to make comparativecast-PUU, toothed belts according to the method of U.S. Pat. No.5,807,194 to Knutson et al. As indicated in Table 6, the treated 12 k−4carbon cords (made from the Toho 12 k yarns of Illustration I) were madeinto 14-mm-pitch HTD®-profile belts. The 14-mm belts of thisillustration utilized the same cast PUU resin formulation for the beltbody as in Illustration I above, i.e., a TDI-terminated polyetherprepolymer based on PTMEG, cured with TMGDAB. As shown in Table 6, the12 k−4 cords of Ex. 11 and 12 showed improved tensile strength over thegreige cords of Comp. Ex. 10. The increase in stiffness relative to the12 k−1 cords of Illustration I is commensurate with the increased corddiameter. The increase in tensile strength of the cords after treatmentis comparable to that observed above in Illustration I. The dip pickupsranged from 10.3 to 14% for this run of 12 k−4 cord. Finally, note thatthe handling testing for the belts of Ex. 11 and 12 again shows dramaticimprovements in tensile strength retained after back bending overpulleys of decreasing size, relative to the Comp. Ex. 10.

TABLE 6 Comp. Ex. 10 Ex. 11 Ex. 12 Carbon Cord 12k-4 12k-4 ConstructionSolids Pick Up (S, Z) — 11, 12.8 (%) Tensile Strength (avg.) 530 926(lb) Stiffness (S, Z) (lbf, — 6.17, 6.22 after 23 d) Belt TensileStrength Made in Cell 3 Cell 1 Tests (14-mm HTD) Cell 3 (lbf/inch beltwidth) Initial Tensile Strength 21308 20469 17657 (inverted on 102-mmdiameter pulleys) After back bends at 43-mm 11441 16526 16763 diameterAfter back bends at 33-mm 8159 13930 15284 diameter After back bends at28-mm 5735 11632 14480 diameter

The results shown in Table 7 indicate that the invention is applicableto making a range of cord sizes, in this illustration from 12 k−1 to 18k−1. The results of Table 7 also show a wide range of solids pickupvalues for the resulting cords, from 6.2% to 17%. In each case, theinventive example cord shows significant improvements in tensilestrength over the greige cord, which is most likely indicative ofimproved handling in the tensile test. It is also noteworthy that thetensile strength of the inventive cords was independent of the solidspickup level, so a single average value is reported for both S and Zcords. Cord stiffness appears to increase with cord size and with solidspickup.

TABLE 7 Comp. Comp. Ex. Ex. Ex. Ex. Comp. Ex. Comp. Ex. 13 14 15 16 Ex.17 18 Ex. 19 20 Carbon Cord Toho Toho Grafil Grafil Grafil Grafil GrafilGrafil Construction 12k-1 12k-1 12k-1 12k-1 15k-1 15k-1 18k-1 18k-1Solids Pick Up (S, Z) — 6.2, — 8.8, — 7.8, — 6.2, (%) 17 12 14.9 15.7Tensile Strength (avg.) 157 281 149 274 216 329 230 380 (lb) Stiffness(S, Z) (lbf, — 0.77, — 0.91, — 1.09, — 1.1, after 23 days) 1.27 1.071.64 1.77

Microscopy was performed on various of the cord examples as prepared andon belt cross sections after casting or forming. The outside of theinventive cord is generally free of a polymeric skin. The outer fibersof the cord generally appear to be well coated with PUU, but notnecessarily bound together, but neither are the outer fibers likely tofly away or fray upon cutting the cord. The inside of the cord isgenerally very well penetrated with PUU adhesive, but not necessarilytotally filled. The belt body material in the cast urethane belts isgenerally able to penetrate the treated cord and almost completely fillthe remaining interstices. This is believed to provide excellentphysical or mechanical adhesion, as well as chemical adhesion. Dependingon treatment conditions, the treated cord may not be as circular incross section as the greige cord due to the drying and polymerization orcuring of the treated cord on a spool. Thus, the invention cord may haveflats formed where it sits upon previous layers of cord due to windingon a spool.

Embodiments of the invention exhibit a number of advantages over theprior art. The invention eliminates cord fraying during cutting andprovides improvements in belt tensile strength, belt bending endurance,and resistance to handling damage. Generally, other physical propertiesof the belt, related to belt performance, have not been negativelyimpacted by the invention. For example, in the case of cast PU belts,flex fatigue resistance and load life capacity of belts of the inventionare as good or slightly better than belts produced from greige cord.Similar advantages should be realized in other reinforced elastomerapplications such as those listed and/or illustrated previously herein.

Although the present invention and its advantages have been described indetail, it should be understood that various changes, substitutions, andalterations can be made herein without departing from the scope of theinvention as defined by the appended claims. Moreover, the scope of thepresent application is not intended to be limited to the particularembodiments of the process, machine, manufacture, composition of matter,means, methods, and steps described in the specification. As one ofordinary skill in the art will readily appreciate from the disclosure ofthe present invention, processes, machines, manufacture, compositions ofmatter, means, methods, or steps, presently existing or later to bedeveloped that perform substantially the same function or achievesubstantially the same result as the corresponding embodiments describedherein may be utilized according to the present invention. Accordingly,the appended claims are intended to include within their scope suchprocesses, machines, manufacture, compositions of matter, means,methods, or steps. The invention disclosed herein may suitably bepracticed in the absence of any element that is not specificallydisclosed herein.

What is claimed is:
 1. A power transmission belt comprising: anelastomeric body, and a tensile cord embedded in the elastomeric body;with the tensile cord impregnated with a polyurea-urethane compositiondifferent from said elastomeric body, said tensile cord comprising thepolyurea reaction product of: a polyurethane prepolymer; and a curativeselected from the group consisting of diamines and water.
 2. The belt ofclaim 1 wherein said composition is a crosslinked polyurea-urethanecomposition.
 3. The belt of claim 2 wherein said tensile cord is atwisted tensile cord and said curative is a diamine.
 4. The belt ofclaim 1 wherein said prepolymer comprises the reaction product of adiisocyanate and one or more polyols selected from the group consistingof polyester polyols, polycarbonate polyols and polyether polyols. 5.The belt of claim 4 wherein said diisocyanate is selected from the groupconsisting of para-phenylene diisocyanate, toluene diisocyanate, and4,4′-methylene diphenyl diisocyanate.
 6. The belt of claim 5 whereinsaid one or more polyols is selected from the group consisting ofpolyether polyols.
 7. The belt of claim 6 wherein said tensile cordcomprises a yarn comprising a plurality of carbon fibers withinterstices between said carbon fibers, and wherein said compositionimpregnates from 20% to 100% of the volume of said interstices and coatssaid carbon fibers.
 8. The belt of claim 1 wherein said prepolymercomprises the reaction product of para-phenylene diisocyanate and apolyether polyol.
 9. The belt of claim 8 wherein said curative is4,4′-methylenebis(3-chloro-2,6-diethylaniline).
 10. The belt of claim 9wherein said elastomeric body comprises cast polyurethane elastomer, andsaid elastomer is in intimate contact with said composition.
 11. Thebelt of claim 10 wherein said tensile cord comprises a yarn comprising aplurality of carbon fibers with interstices between said carbon fibers,and wherein said composition impregnates from 20% to 99% of the volumeof said interstices and coats said carbon fibers; and wherein saidelastomer impregnates at least a portion of the remainder of saidinterstices.
 12. The belt of claim 1 wherein said elastomeric bodycomprises vulcanized rubber.
 13. The belt of claim 1 wherein saidelastomeric body comprises a thermoplastic elastomer and said elastomeris in intimate contact with said polyurea-urethane composition.
 14. Thebelt of claim 13 wherein said elastomer is a thermoplastic polyurethane.15. The belt of claim 1 wherein the polyurethane prepolymer hasisocyanate end groups that are blocked with a blocking agent.
 16. Thebelt of claim 4 wherein said diisocyanate comprises para-phenylenediisocyanate, toluene diisocyanate, or both, and wherein said polyolcomprises a polyether polyol.
 17. The belt of claim 16, wherein saidpolyether polyol comprises polytetramethylene ether glycol.
 18. The beltof claim 4, wherein said diisocyanate comprises isophorone diisocyanate,hexamethylene diisocyanate, or both, and wherein said polyol comprises apolyether polyol.
 19. The belt of claim 18, wherein said polyetherpolyol comprises polytetramethylene ether glycol.